The present invention relates to an angular velocity detection apparatus and an electronic instrument.
An electronic instrument or a system that includes an angular velocity detection apparatus, and performs a predetermined control process based on the angular velocity detected by the angular velocity detection apparatus has been widely used. For example, a vehicle travel control system prevents a side skid, or detects an overturn, based on the angular velocity detected by the angular velocity detection apparatus.
Such an electronic instrument or system performs wrong control if the angular velocity detection apparatus breaks down. Therefore, measures such as lighting an alarm lamp when the angular velocity detection apparatus has broken down have been employed. Various technologies that diagnose failure of the angular velocity detection apparatus have been proposed. For example, JP-A-2000-171257 focuses on the fact that a signal output from the vibrator of the angular velocity detection apparatus includes an angular velocity component, and a self-vibration component (vibration leakage component) based on excited vibrations of the vibrator, and discloses method that determines the presence or absence of failure of the angular velocity detection apparatus by extracting the vibration leakage component from the signal output from the vibrator, and monitoring the amplitude of the vibration leakage component. JP-A-2010-107416 discloses a failure diagnosis method that reliably generates a self-vibration component by tuning the balance so that the vibration energy of the vibrator becomes imbalanced.
It is ideal that a circuit that extracts the angular velocity component not to extract the vibration leakage component. However, a phase shift of a synchronous detection clock signal occurs due to a circuit production variation, so that the vibration leakage component is included in the extracted angular velocity signal (gyro signal). Therefore, if the vibration leakage component is enhanced as disclosed in JP-A-2010-107416, the temperature characteristics of the angular velocity signal deteriorate due to the effect of the temperature characteristics of the vibration leakage component. If the temperature characteristics of the vibration leakage component are indicated by a linear function or a quadratic function, the temperature characteristics of the vibration leakage component can be corrected using a small-scale temperature compensation circuit. However, the vibration leakage component has temperature characteristics indicated by a higher-order function. The circuit scale necessarily increases when correcting the temperature characteristics of the vibration leakage component using a higher-order function circuit.